Did you try enabling vsync? Because that could really make a big difference.
Apart from that, it might be a good idea to improve your cooling, or underclock your components. Games don't exactly get to tell your computer how much power it should draw. The developers could insert random delays to help systems with inadequate cooling idle a little, but that would reduce performance for everybody.
What the fuck, inexile? It's an isometric RPG. It looks *worse* than Baldur's Gate II.
The technology used is completely different though. You are of course right to have a subjective opinion on the visual quality. But comparing a 3D scene that enables lots of fully dynamic effects to a pre-rendered backdrop is as much apples-vs-oranges as comparing a realtime render to a recorded cinema movie.
At release, the game was playable (though a little sluggish) on my fanless mini-pc with intel integrated graphics. That's pretty good for such a new release; most games that come out these days would be nigh unplayable on such a system. Now take a look at the changelog, and you'll see that they've worked on plenty of performance improvements. They're trying, and I don't think it helps to get angry about it.
Also, they did not write the engine. The game is built on unity.